A retinal biophysicist proposes to continue investigations of signal processing by retinal cells in amphibia and fish. The proposed investigations are framed in terms of a theory of processing in which response properties of various cells have been optimized by evolution for transmitting the information contained in the retinal images of real visual scenes in the organisms world, subject to the sampling and noise limitations imposed by photoreceptors; the noise includes specifically the dark "shot" and "continuous" noise of rods. The theory is presented as generating seven specific testable hypothesis, and experimental tests of these hypothesis are proposed. In essence, the theory views the retina as a maximum fidelity, minimum loss set of linear filters, whose output is quantized in a optimal way by the ganglion cells.